Base transceiver stations, known in the art and illustrated 102 in FIG. 1, are used for example in Universal Mobile Telecommunications System (UMTS), where they are known as Node Bs. Node B consists of an indoor equipment or indoor units (IDUs), 104 in form of a shelf with cards for controller units and radio intermediate frequency units (one set of these is required per carrier), Asynchronous Transfer Mode (ATM) switching units etc., and an outdoor equipment or outdoor units (ODUs) 108 for the mobile radio connectivity, i.e. radio transceivers and sector antennas, e.g. for 120° sectorization, connected to each other by means of intermediate-frequency (IF) cables 116. There are also known in the art other sectorizations e.g. 1×360° (omnidirectional). The maximum data rate of UMTS carriers with 5 MHz bandwidth is in the order of 2-15 Mbit/s dependent on the implemented UMTS technology, e.g. R'99, High Speed Downlink Packet Access (HSDPA) or even more in the future. The data traffic from UMTS frequency carriers is aggregated in the Asynchronous Transfer Mode (ATM) switch integrated in the indoor unit 104 using statistical multiplexing gain for bursty traffic profiles in order to reduce the required backhaul capacity. However, when in UMTS system the Wideband-Code-Division Multiple Access (W-CDMA) air interface is highly utilised, i.e. the statistical multiplexing gain is low, the maximum required backhaul capacity for a 2×5 MHz carrier Node B consisting of 3×120° sectors will be in the order of 84 Mbit/s, i.e. 6×14 Mbit/s (there are two carriers of 5 MHz bandwidth each in one 120° sector). In this situation there is no big potential for further multiplexing gain. This traffic can be transported to a radio network controller (RNC) or the next ATM aggregation node by a fixed radio point-to-point (PtP) system (or by a fixed radio point-to-multipoint (PmP) system) consisting of an indoor unit (IDU) 106 and outdoor unit (ODU) 120 with a directional antenna on the base station side to another directional antenna 112 on the other side of the link 110 connected to a corresponding IDU (not shown).
Apart from the ineffective, in some cases, statistical multiplexing another disadvantage of the solutions known in the art is that the indoor equipment at the base transceiver station requires either a telecommunications room, which is rented in most cases, or a shelter on the roof including air conditioning etc. Cables have to be mounted between indoor and outdoor equipment. For repair and maintenance activities service staff has to travel to these sites, which are fairly distributed in the service area, in order to achieve sufficient coverage and capacity and this is very expensive.
Hence, an improved base transceiver station would be advantageous and in particular one that does not require indoor equipment.